All-season tires and studless tires include, in their treads, multiple partitioned land sections each formed of a block or a rib, and multiple sipes are formed in each of the land sections. In order for such a pneumatic tire to achieve sufficient ice performance while the tire is brand-new and hence cannot obtain inherent properties of rubber, multiple narrow grooves each being shallower than a sipe are provided in a ground contact surface of each land section (see, for example, Patent Document 1).
The above-mentioned narrow grooves are generally arranged at certain pitches in a certain direction in the ground contact surface of each land section. When such narrow grooves are provided in the ground contact surface of each land section, the pneumatic tire achieves excellent ice performance due to edge effect and drainage effect of the narrow grooves while the tire is brand-new, and starts to achieve excellent ice performance due to the inherent properties of rubber by the time all the narrow grooves are worn out.
However, in these years, such pneumatic tires have been desired to have further improved ice performance while they are brand-new, and sufficient ice performance is not currently always achieved with the conventional narrow groves.